The 14"/50 caliber gun was a naval gun mounted on New Mexico- and Tennessee-classbattleships. These ships also featured the first "three-gun" turrets, meaning that each gun in each turret could be "individually sleeved" to elevate separately (however, they could be linked so they would elevate as a unit, similar to the triple turrets on other Navy ships). The 14"/50 caliber guns were designated as Mark 4 and 6, with later versions known as Mark 7, 11, and B. These guns were more powerful than the main gun mounted on the previous two classes of US battleships (the Nevada and Pennsylvania classes), the 14"/45 caliber gun.[1]

The 14"/50 caliber gun was designed in 1916 and entered service in 1918 on the New Mexico-class battleships. The guns were capable of firing a 1,402 pounds (636 kg) armor-piercing (AP) projectile at an angle of 15 degrees, to a range of 24,000 yards (22 km). Each gun weighed approximately 179,614 pounds (81.472 Mg), including the breech, and was 714 inches (18.1 m) long. The propellant charge used for the ammunition weighed 470 pounds (210 kg) and was contained in four bags.[1]

Each Mark 4 built-up gun consisted of a tube, liner, and a screw box liner with a separate screwed-on flange. Three hoops and two locking rings were also included. The Mark 6 was slightly different in that it contained a single step taper liner and uniform twist rifling. Downward-opening Welin breech blocks and Smith-Asbury mechanisms were used on both Mark 4 and Mark 6 types. The Navy encountered dispersion problems at extreme ranges with these guns in the 1920s. Several methods were used to correct these problems, including correction of range tables for errors, addition delay coils, reduction of chamber volume, and improvement of shot seating.[1]

The Mark 7 was designed in the 1930s and entered service in 1935. This gun included a smaller chamber, a shell-centering cone, a single-slope band seat, uniform rifling, and a tube locking ring. Mark 11 was introduced later, with chromium plating added to the bore. New Mexico- and Tennessee-class battleships were rearmed with 14"/50 Mark 11 guns, with the Tennessee receiving the upgrade in 1942. The dispersion problems that existed with Marks 4 and 6 were corrected with these guns.[4]

A newer version of the 14"/50 caliber gun, Mark B, was designed in 1937. It was the original gun intended for use on the North Carolina-class battleships. Although it was simpler and lighter than the older versions, the Mark B was the most powerful 14 inch weapon ever designed by the United States. However, the prototype of this gun was not completed because the 14 inch treaty limit was rescinded in 1937 which allowed the new battleships to be armed with 16 inch guns.[4]